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  <div class="section" id="module-trace">
<h1>27.7. <tt class="xref docutils literal"><span class="pre">trace</span></tt> &#8212; Trace or track Python statement execution<a class="headerlink" href="#module-trace" title="Permalink to this headline">¶</a></h1>
<p>The <tt class="xref docutils literal"><span class="pre">trace</span></tt> module allows you to trace program execution, generate
annotated statement coverage listings, print caller/callee relationships and
list functions executed during a program run.  It can be used in another program
or from the command line.</p>
<div class="section" id="command-line-usage">
<span id="trace-cli"></span><h2>27.7.1. Command Line Usage<a class="headerlink" href="#command-line-usage" title="Permalink to this headline">¶</a></h2>
<p>The <tt class="xref docutils literal"><span class="pre">trace</span></tt> module can be invoked from the command line.  It can be as
simple as</p>
<div class="highlight-python"><pre>python -m trace --count somefile.py ...</pre>
</div>
<p>The above will generate annotated listings of all Python modules imported during
the execution of <tt class="docutils literal"><span class="pre">somefile.py</span></tt>.</p>
<p>The following command-line arguments are supported:</p>
<dl class="docutils">
<dt><em class="xref">--trace</em>, <a class="reference external" href="../using/cmdline.html#cmdoption-t"><em class="xref">-t</em></a></dt>
<dd>Display lines as they are executed.</dd>
<dt><em class="xref">--count</em>, <a class="reference external" href="../using/cmdline.html#cmdoption-c"><em class="xref">-c</em></a></dt>
<dd>Produce a set of  annotated listing files upon program completion that shows how
many times each statement was executed.</dd>
<dt><em class="xref">--report</em>, <em class="xref">-r</em></dt>
<dd>Produce an annotated list from an earlier program run that used the
<em class="xref">--count</em> and <em class="xref">--file</em> arguments.</dd>
<dt><em class="xref">--no-report</em>, <em class="xref">-R</em></dt>
<dd>Do not generate annotated listings.  This is useful if you intend to make
several runs with <em class="xref">--count</em> then produce a single set of annotated
listings at the end.</dd>
<dt><em class="xref">--listfuncs</em>, <em class="xref">-l</em></dt>
<dd>List the functions executed by running the program.</dd>
<dt><em class="xref">--trackcalls</em>, <em class="xref">-T</em></dt>
<dd>Generate calling relationships exposed by running the program.</dd>
<dt><em class="xref">--file</em>, <em class="xref">-f</em></dt>
<dd>Name a file containing (or to contain) counts.</dd>
<dt><em class="xref">--coverdir</em>, <em class="xref">-C</em></dt>
<dd>Name a directory in which to save annotated listing files.</dd>
<dt><em class="xref">--missing</em>, <a class="reference external" href="../using/cmdline.html#cmdoption-m"><em class="xref">-m</em></a></dt>
<dd>When generating annotated listings, mark lines which were not executed with
&#8216;<tt class="docutils literal"><span class="pre">&gt;&gt;&gt;&gt;&gt;&gt;</span></tt>&#8216;.</dd>
<dt><em class="xref">--summary</em>, <a class="reference external" href="../using/cmdline.html#cmdoption-s"><em class="xref">-s</em></a></dt>
<dd>When using <em class="xref">--count</em> or <em class="xref">--report</em>, write a brief summary to
stdout for each file processed.</dd>
<dt><em class="xref">--ignore-module</em></dt>
<dd>Accepts comma separated list of module names. Ignore each of the named
module and its submodules (if it is a package).  May be given
multiple times.</dd>
<dt><em class="xref">--ignore-dir</em></dt>
<dd>Ignore all modules and packages in the named directory and subdirectories
(multiple directories can be joined by os.pathsep).  May be given multiple
times.</dd>
</dl>
</div>
<div class="section" id="programming-interface">
<span id="trace-api"></span><h2>27.7.2. Programming Interface<a class="headerlink" href="#programming-interface" title="Permalink to this headline">¶</a></h2>
<dl class="class">
<dt id="trace.Trace">
<em class="property">
class </em><tt class="descclassname">trace.</tt><tt class="descname">Trace</tt><big>(</big><span class="optional">[</span><em>count=1</em><span class="optional">[</span>, <em>trace=1</em><span class="optional">[</span>, <em>countfuncs=0</em><span class="optional">[</span>, <em>countcallers=0</em><span class="optional">[</span>, <em>ignoremods=()</em><span class="optional">[</span>, <em>ignoredirs=()</em><span class="optional">[</span>, <em>infile=None</em><span class="optional">[</span>, <em>outfile=None</em><span class="optional">[</span>, <em>timing=False</em><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><big>)</big><a class="headerlink" href="#trace.Trace" title="Permalink to this definition">¶</a></dt>
<dd>Create an object to trace execution of a single statement or expression. All
parameters are optional.  <em>count</em> enables counting of line numbers. <em>trace</em>
enables line execution tracing.  <em>countfuncs</em> enables listing of the functions
called during the run.  <em>countcallers</em> enables call relationship tracking.
<em>ignoremods</em> is a list of modules or packages to ignore.  <em>ignoredirs</em> is a list
of directories whose modules or packages should be ignored.  <em>infile</em> is the
file from which to read stored count information.  <em>outfile</em> is a file in which
to write updated count information. <em>timing</em> enables a timestamp relative
to when tracing was started to be displayed.</dd></dl>

<dl class="method">
<dt id="trace.Trace.run">
<tt class="descclassname">Trace.</tt><tt class="descname">run</tt><big>(</big><em>cmd</em><big>)</big><a class="headerlink" href="#trace.Trace.run" title="Permalink to this definition">¶</a></dt>
<dd>Run <em>cmd</em> under control of the Trace object with the current tracing parameters.</dd></dl>

<dl class="method">
<dt id="trace.Trace.runctx">
<tt class="descclassname">Trace.</tt><tt class="descname">runctx</tt><big>(</big><em>cmd</em><span class="optional">[</span>, <em>globals=None</em><span class="optional">[</span>, <em>locals=None</em><span class="optional">]</span><span class="optional">]</span><big>)</big><a class="headerlink" href="#trace.Trace.runctx" title="Permalink to this definition">¶</a></dt>
<dd>Run <em>cmd</em> under control of the Trace object with the current tracing parameters
in the defined global and local environments.  If not defined, <em>globals</em> and
<em>locals</em> default to empty dictionaries.</dd></dl>

<dl class="method">
<dt id="trace.Trace.runfunc">
<tt class="descclassname">Trace.</tt><tt class="descname">runfunc</tt><big>(</big><em>func</em>, <em>*args</em>, <em>**kwds</em><big>)</big><a class="headerlink" href="#trace.Trace.runfunc" title="Permalink to this definition">¶</a></dt>
<dd>Call <em>func</em> with the given arguments under control of the <a title="trace.Trace" class="reference internal" href="#trace.Trace"><tt class="xref docutils literal"><span class="pre">Trace</span></tt></a> object
with the current tracing parameters.</dd></dl>

<p>This is a simple example showing the use of this module:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">sys</span>
<span class="kn">import</span> <span class="nn">trace</span>

<span class="c"># create a Trace object, telling it what to ignore, and whether to</span>
<span class="c"># do tracing or line-counting or both.</span>
<span class="n">tracer</span> <span class="o">=</span> <span class="n">trace</span><span class="o">.</span><span class="n">Trace</span><span class="p">(</span>
    <span class="n">ignoredirs</span><span class="o">=</span><span class="p">[</span><span class="n">sys</span><span class="o">.</span><span class="n">prefix</span><span class="p">,</span> <span class="n">sys</span><span class="o">.</span><span class="n">exec_prefix</span><span class="p">],</span>
    <span class="n">trace</span><span class="o">=</span><span class="mf">0</span><span class="p">,</span>
    <span class="n">count</span><span class="o">=</span><span class="mf">1</span><span class="p">)</span>

<span class="c"># run the new command using the given tracer</span>
<span class="n">tracer</span><span class="o">.</span><span class="n">run</span><span class="p">(</span><span class="s">&#39;main()&#39;</span><span class="p">)</span>

<span class="c"># make a report, placing output in /tmp</span>
<span class="n">r</span> <span class="o">=</span> <span class="n">tracer</span><span class="o">.</span><span class="n">results</span><span class="p">()</span>
<span class="n">r</span><span class="o">.</span><span class="n">write_results</span><span class="p">(</span><span class="n">show_missing</span><span class="o">=</span><span class="bp">True</span><span class="p">,</span> <span class="n">coverdir</span><span class="o">=</span><span class="s">&quot;/tmp&quot;</span><span class="p">)</span>
</pre></div>
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            <ul>
<li><a class="reference external" href="">27.7. <tt class="docutils literal"><span class="pre">trace</span></tt> &#8212; Trace or track Python statement execution</a><ul>
<li><a class="reference external" href="#command-line-usage">27.7.1. Command Line Usage</a></li>
<li><a class="reference external" href="#programming-interface">27.7.2. Programming Interface</a></li>
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